Recently, as a light source of a backlight of an LCD, LEDs have come to be used instead of a conventional cold cathode fluorescent lamp (CCFL). As for the LCDs, however, higher brightness LEDs are desired. To meet this, LED backlights have been developed which have a plurality of LED lines, each of which includes a plurality of LEDs connected in series. Such an LED backlight adjusts the emission quantity of the LEDs by carrying out PWM (Pulse Width Modulation) control of a current supplied to each LED line from a power supply via a power feed line. However, when driving all the LED lines with a driving signal having the same waveform, a large current flows instantaneously, thereby inducing ripples on the power feed line, which causes screen noise and the like.
As a technique for solving such a problem, Patent Document 1 discloses a display unit that improves display characteristics by reducing a current ripple component. The display unit has a plurality of power driving sections for supplying prescribed driving power to the light source, and a control section for controlling the plurality of power driving sections in such a manner that the currents output from the individual power driving sections have a prescribed phase difference.
Patent Document 1: Japanese Patent Laid-Open No. 2007-80819.
The technique disclosed in the foregoing Patent Document 1 requires a plurality of power driving sections for each LED line. Accordingly, trying to provide a plurality of LED lines to achieve the high brightness necessitates a great number of power driving sections, thereby offering problems of requiring a large mounting area and increasing the cost.
The present invention is implemented to solve the foregoing problems. Therefore it is an object of the present invention to provide an inexpensive LED backlight drive capable of driving the LED backlight with a simple configuration.